1. Field of the Invention
The present invention relates to a sealing structure in a direct acting type auto-by starter. In particular, the present invention relates to an improvement in a sealing structure for preventing the entry of liquid such as water into the auto-by starter due to pressure fluctuations in the auto-by starter associated with the movement of a starting valve provided in the auto-by starter.
2. Descritption of Related Art
An auto-by starter for facilitating the starting of an internal combustion engine is well known in the art as described in Japanese Patent Laid-open No. Hei 10-30501 and Japanese Utility Model Laid-open No. Sho 63-71458, for example. When starting an engine, a starting valve provided in the auto-by starter is operated to open a starting intake passage leading to the engine, thereby sucking the outside air. At the same time, fuel is supplied through a jet needle into the starting intake passage by utilizing vacuum in this passage, thereby producing a considerably concentrated air-fuel mixture, which is then supplied to a combustion chamber of the engine.
In a well-known type of auto-by starter, the starting valve is automatically operated by using wax having a temperature dependence. As another type of auto-by starter, a direct acting type auto-by starter includes a manually operated starting valve. The starting valve is operated by manipulating a lever.
FIGS. 6(a), 6(b), and 6(c) illustrate the operation of a direct acting type auto-by starter 010 in the background art. The structure of the auto-by starter 010 is schematically shown. The auto-by starter 010 has a sliding hole structure 01a formed in a carburetor body. A starting valve 02 is vertically movable in the sliding hole structure 01a by operating a manual lever (not shown). A jet needle 02g is mounted at a lower portion of the starting valve 02. When the starting valve 02 is moved upward against a spring member (not shown) by the operation of the manual lever, a starting intake passage 01c is opened by the starting valve 02 to allow induction of air through the starting intake passage 01c. At this time, fuel is supplied through the jet needle 02g into the starting intake passage 01c by vacuum in the passage 01c, thereby producing a thick air-fuel mixture, which is then introduced into a combustion chamber of the engine.
The starting valve 02 has a stem 02a slidably supported in a retainer 03. An upper portion 02b of the stem 02a projects upward from the retainer 03. With the vertical movement of the starting valve 02, the upper portion 02b of the stem 02a comes into sliding contact with a sealing portion 05a of a sealing member 05 mounted on the retainer 03.
The volume of an internal operating space in the auto-by starter 010 changes with the upward movement of the starting valve 02 by the operation of the manual lever (see FIG. 6(b)) or with the downward movement of the starting valve 02 by the operation of the spring member (see FIG. 6(a) or 6(c)), resulting in pressure fluctuations in the internal operating space. More specifically, the volume of a sliding space 02f for the starting valve 02 in the auto-by starter 010 decreases with the upward movement of the starting valve 02, causing an increase in pressure in the sliding space 02f (see FIG. 6(b)), whereas the volume of the sliding space 02f increases with the downward movement of the starting valve 02, causing a decrease in pressure in the sliding space 02f (see FIG. 6(a) or 6(c)). Such pressure fluctuations due to the changes in volume of the sliding space 02f cause a phenomenon such that gas inside the auto-by starter 010 flows out of the operating space (see FIG. 6(b)) and gas outside the auto-by starter 010 flows into the operating space (see FIG. 6(c)).
The gas flow out of the auto-by starter 010 and the gas flow into the auto-by starter 010 are made through the sealing portion 05a of the sealing member 05, which is kept in sliding contact with the upper portion 02b of the starting valve 02.
In the direct acting type auto-by starter 010 mentioned above, the flow of outside gas (ambient air) into the auto-by starter 010 or the flow of inside gas out of the auto-by starter 010 due to the pressure fluctuations in the auto-by starter 010 associated with the vertical movement of the starting valve 02 is repeatedly made. Accordingly, especially when the inside gas flows out of the auto-by starter 010, the upper end of the sealing portion 05a of the sealing member 05 is opened, or separated from the stem 02a by the discharge pressure of the inside gas, causing the production of a gap between the sealing portion 05a and the stem 02a. As a result, there is a possibility that water such as rainwater may enter the auto-by starter 010 through this gap. Furthermore, when the flow of moist ambient air into the auto-by starter 010 is repeated, liquid such as water contained in the moist ambient air may stay inside the auto-by starter 010.
The liquid staying inside the auto-by starter 010 is hard to expel to the outside of the auto-by starter 010, so that there is a possibility of formation of rust on the starting valve 02 and the inner surface of the sliding space 02f due to this liquid, causing interference with a smooth operation of the starting valve 02. Moreover, there is a possibility of freezing of this liquid in winter, causing a malfunction of the starting valve 02 operated by the manual lever. As a result, the auto-by starter for the engine cannot function sufficiently.
Thus, the gas flow through the sealing portion 05a due to the pressure fluctuations in the direct acting type auto-by starter 010 associated with the operation of the starting valve 02 as well as the entry of water such as rainwater through the sealing portion 05a into the auto-by starter 010 is a problem that cannot be ignored. It is therefore necessary to take action against the above problem. It is accordingly an object of the present invention to provide an improvement in the sealing structure 05 in the auto-by starter 010, which can solve the above problem.